The present invention relates to pintle valves for permitting the controlled admission of exhaust gases into the fuel intake manifold of an internal combustion engine; more particularly, to the pintle bearing, bearing retaining spring, and bearing splash shield of such a valve; and most particularly to a modular subassembly which may be pre-assembled and which combines these three components for ease of manufacture of the valve, reduction in assembly errors, and reduced cost of manufacture.
It is well known in the automotive art to provide a variable valve connecting the exhaust manifold with the intake manifold of an internal combustion engine to permit selective and controlled recirculation of a portion of an engine""s exhaust gas into the fuel intake stream. Such recirculation is beneficial for reducing the burn temperature of the fuel mix in the engine to reduce formation of nitrogen and sulfur oxides which are significant components of smog. Such a valve is known in the art as an exhaust gas recirculation (EGR) valve. Typically, an EGR valve has a valve body enclosing a chamber disposed between a first port in the exhaust manifold and a second port in the intake manifold; a valve seat dividing the chamber between the two ports; a pintle valve having a valve head fitted to the valve seat and a valve stem or pintle extending from the valve head through a bearing mounted in a third port in a sidewall of the valve body; and a solenoid actuator mounted on the exterior of the valve body and operationally connected to the outer end of the valve stem. Because exhaust gas may leak along the valve stem, the actuator typically is mounted on standoffs to vent such leaking exhaust gas and thereby prevent it from entering and corroding the solenoid. The bearing has a circumferential flange for sealing against an outer surface of the valve body and may be urged to seal by a spring which is compressed and captured between the valve body and the actuator, such as a compressed coil spring surrounding the valve stem. An EGR valve having such a standoff configuration may be exposed to various environmental hazards, such as mud and salt from roadways, which can corrode the exposed valve stem and spring or accumulate on the bearing, eventually fouling the stem and disabling the valve. Therefore, a cup-shaped bearing splash shield extending axially over the spring and bearing typically is provided to protect the bearing, stem, and spring from external contamination.
During assembly of such a prior art valve, after the valve head is inserted into the chamber via the third port, the bearing is threaded onto the pintle and seated against the valve body, then the spring is installed onto the pintle, then the splash shield is installed over the spring, and then the actuator pole piece is attached to the outer end of the pintle and the actuator is bolted to the valve body through a plurality of hollow standoffs, thus capturing the spring against the underside of the shield and compressing the spring to the proper degree. This procedure requires manual alignment of the various parts, which are loose and which must be mutually aligned for proper assembly; thus, the valve is easily subject to misassembly.
What is needed is a modular subassembly of the bearing, spring, and shield which is readily pre-assembled offline, which is self-aligned by the pintle; in which the spring is preloaded to a predetermined and repeatable compression; and which is readily installed as a single component on the valve pintle by an assembly operator.
The present invention is directed to a subassembly module comprising a pintle bearing, bearing retaining spring, and bearing splash shield for an exhaust gas recirculation valve for an internal combustion engine. The bearing is provided with a circumferential flange for sealing on an axial face thereof with an outer surface of the valve body, and with an annular step for receiving the rolled or crimped skirt of the bearing splash shield. The bearing retaining spring surrounding the valve pintle is compressed and captured within the splash shield as the skirt is formed onto the annular step to form the module. The axial length of the module between the outer end of the shield and the axial face of the bearing flange is slightly greater than the assembled distance between the valve body and the actuator of the EGR valve, such that the spring is further compressed by installation of the actuator onto the valve body to urge the first circumferential bearing face sealingly against the valve body. Advantageously, the subassembly may be pre-assembled offline by known methods to reduce complexity during assembly of the valve.